Revenue from Contracts with Customers and Lease Income - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 2,571	$ 2,504
Contract Assets	81	117
Contract Liabilities	72	57
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	616	589
Contract Assets	2	2
Contract Liabilities	3	4
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	695	736
Contract Assets	31	63
Contract Liabilities	13	14
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	85	73
Contract Assets	0	0
Contract Liabilities	2	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	128	149
Contract Assets	0	1
Contract Liabilities	1	1
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivable	865	753
Contract Assets	0	0
Contract Liabilities	$ 0	$ 0